Effects of membrane depolarization on intracellular calcium in single nerve terminals.
The [Ca2+]i of individual neurosecretory nerve terminals loaded with the fluorescent probe fura-2 was monitored during depolarizing stimuli and in the presence of substances known to induce or block neurohormone release. Induction of membrane depolarization with elevated [K+] or veratridine led to a rapid increase in [Ca2+]i that was sensitive to block by substances which block voltage-sensitive L-type Ca2+ channels such as the dihydropyridine nicardipine and by D-888. Relaxin, cholecystokinin and enkephalin which have been reported to regulate vasopressin and oxytocin secretion at the nerve endings were without effect on basal [Ca2+]i or K(+)-stimulated increases in [Ca2+]i.
Stuenkel
E L
EL
Department of Physiology, University of Michigan, Ann Arbor 48109.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002766:Cholecystokinin / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009411:Nerve Endings / Q000187:drug effects / Q000502:physiology*; D009529:Nicardipine / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012065:Relaxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D004745:Enkephalins; D010456:Peptides, Cyclic; D020960:omega-Conotoxins; C053423:Conus magus toxin; D014701:Veratridine; D012065:Relaxin; D002766:Cholecystokinin; D009529:Nicardipine; D011188:Potassium; D002118:Calcium